I am convinced that it is soot build up in these rocker shaft that causes the uneven wear, then the geometry gets out of whack and the lobes get scarred. If it was a bad or unbalanced cam, it would show itself much earlier in the engine's life, and if it was a manufacturer defect there would likely be recalls or TSBs. When the overhead is adjusted and the cam is unbalanced, uneven wear, etc, it seems like there would be a noticeable discrepancy in the amount of adjustments, or that the same lobe would continually be the issue on each D13.
Yup soot kills them... Big culprit is so many running the older oils (15-40) that are too heavy and don't flow very well as they get loaded up with soot. If you've got soot buildup you need to change oil sooner and you should be using a 10-30 or 5-30 in a Volvo motor as well... Also good to consider the oil brand and type... Not all are the same. Probably the worst is white bottle Rotella 15-40. Another reason for synthetics... They keep the engine cleaner! .
I agree with the soot as well. The way the oil comes out and how black it is even after 20,000 miles is unbelievable.
Yup it's really bad how dirty they are... Synthetic oils and lighter 10-30s help flow and keeping the internals cleaner
I've heard this about rotella which is all i use in my truck i have one with a D12 it's up to 1.6 mil no issues i did the rods on the main at 1.5 just because it was way overdue no signs of any weird wear #### it looked better than series 60 at 700K the only think i do different is that it gets an oil change every 11 to 13 K like clockwork other than that no oil consumption and it runs like a champ. I used to use Delvac but my truck kept having about a gall topoff at 10 K Been using rotella for years and no problems with it whatsoever, also personally not a big fan of synthetics mainly cuz i run older trucks like 05 to 07 and they have minor leaks if i switch them to synthetic they would drip oil all over the place.
Or wow yes that is very early oil changes. Yeah Volvo is a great motor compared to the Detroit S60 in terms of strength, life.
this is how i keep my trucks nice with no issues i've never really believed in 25k or 30 k oil intervals just not a big fan of them this way i can even look at the truck and see if something is about to go bad more often